Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual semana tem uma frequência de 51.558?
 ###Tabelas: CREATE TABLE regular_season (regular_season_id AUTO_INCREMENT PRIMARY KEY, Week INT, Date VARCHAR, Opponent VARCHAR, Result VARCHAR, Attendance INT) CREATE TABLE locomotives_and_rolling_stock (locomotives_and_rolling_stock_id AUTO_INCREMENT PRIMARY KEY, Number VARCHAR, TMS Number VARCHAR, Builder VARCHAR, Year built INT, Carriage type VARCHAR) CREATE TABLE fastest_progress_to_top_division (fastest_progress_to_top_division_id AUTO_INCREMENT PRIMARY KEY, Name VARCHAR, Tournaments INT, Pro Debut VARCHAR, Top division debut VARCHAR, Highest rank VARCHAR) CREATE TABLE doubles_statistics (doubles_statistics_id AUTO_INCREMENT PRIMARY KEY, Tournament VARCHAR, 2006 VARCHAR, 2007 VARCHAR, 2008 VARCHAR, 2009 VARCHAR, 2010 VARCHAR, 2011 VARCHAR, 2012 VARCHAR) CREATE TABLE siena_college_research_institute_survey (siena_college_research_institute_survey_id AUTO_INCREMENT PRIMARY KEY, Seq. VARCHAR, Name VARCHAR, Background INT, Party Leadership INT, Communication Ability INT, Relations with Congress INT, Court Appointments INT, Handling of Economy INT, Luck INT, Ability to Compromise INT, Willing to take Risks INT, Executive Appointments INT, Overall Ability INT, Imagination INT, Domestic Accomplishments INT, Integrity INT, Executive Ability INT, Foreign Policy Accomplishments INT, Leadership Ability INT, Intelligence INT, Avoid Crucial Mistakes INT, Expert's View INT, Overall INT)  
SELECT MIN Week FROM regular_season WHERE Attendance = 51,558